Method of and apparatus for melting glass



Patented Feb. 14, 1933 IUNITED s'ra'ras PATENT oFFlcE HAROLDA. WADHAN,`OF HARTFORD, CONNECTICUT, ASSIGNOR TO HARTFORD-EMPIRE COMPANYLOF HARTFORD, CONNECTICUT, A CORPORATION OF DELAWARE METHOD OF AND APPARATUS FOB MELTING vGLASS Application mea 'may s, 1930. .semi m. 450,071.

This invention relates to a method of and alpparatus for melting glass by the use of e ectricity, and relates more lparticularly to a new method for starting such an operation and to apparatus to be used in connection with such a method.

In melting glass by passing a current of electricity therethrough, it has been found that for various reasons the most satisfactory electrodes are those made of graphite. These present the inherent vdisadvantage of oxidizing at the temperature of molten glass if they are in lcontact with air. The oxidation results in adiscoloration of the glass and makes itV unsuitable for many uses as well as the burning of the electrodesy and consequent reduction in size thereof, which is harmful. f

Since glass is a conductor of electricity only when heated, the problem of starting the operation of an electrically operated tank in w ich glass is itself used as a. resistor is presented. Either cullet must be melted in place between the electrodes by supplemental eating means to heat it to a temperature at which it will conduct 'a current or else molten glass must be poured into the tank to form a connection between the electrodes. With the apparatus now in use the first method allows oxidation of the electrodes due to the fact that a quantity of air is incorporated in the cullet and considerable time must elapse before the cullet is so fused that it will preclude the admission of air to the electrodes while at the same time the temperature is suliiciently high to oxidize the electrodes. The second method allows oxidation primarily due to the construction of the tank which is usually of such size for practica-l use that considerable time must elapse before suflicient glass can be ladled into the tank to make the depth of the glass therein sufficient to cover the electrodes. It follows that in order to manufacture glass which is free of the discoloration caused by the oxidation of the electrodes, much glass must be gradually withdrawn and its place taken with batch or cullet which is melted in its place.

This process must continue gradually until the discoloration of the glass in the tank has been reduced to the point where it is negligible. It is, of course, under this procedure theoretically impossible to eliminate all dis- -colorations from the glass, and as a practical matter the expense of proceeding 1n this way, due to the large quantities of glass which must be Withdrawn and the length of time which it takes to s'upply additional batch or cullet to the glass in the tank while keeping the electrodes entirely submerged and drawing oi the discolored glass, is so great as to make it relatively worthless.

In the melting of glass there are found frequently varying temperatures at any given section thereof. This results in glass having undesirable characteristics being taken from the tank at the outlet. It is, therefore, often highly desirable to move the electrodes vertically'within the furnace in order to change the path through which the current passes and to thuscompensate for` variations in the temperatures of various portions of a given section. The most satisfactory Way of doing this is to support the electrode from the top of the tank and thus the stem of the electrode is from time to time moved to vario'us depths in the bath of glass. It is, therefore, desirable in order to preclude the oxidation of the stem at the glass line to protect it from contact with the air. In order to do this, I have therefore devised a new type of protected electrode.

An object of this invention is to provide a method of melting glass whereby the wastage previously occurring in the production of uncolored` glass heretofore used may he avoided.

Another object is to provide a glass melting tank forl carrying out the above-mentioned method.

Another object is to provide an electrode which may be moved vertically within the furnace and all portions of which may be protected against oxidation when at the glass line.

A more specific object of my invention is to provide a method of starting the operation of a glass melting tank in which oxidation of the electrodes will be prevented and thus the tion eliminated.

discoloration o'f Still another object of'm invention 'is to provide an electrode whic will be maintained at all times out of contact with -air 1n such placesv and at such tem eratures as would cause the oxidation thereo Referring to the drawing, Fi ure 1 is a horizontal sectional iriew showing va glass melting tank embodying my inventlon; v A p Fi 2 is a vertical sectional-view taken on the lines 2-2 of Fig. 1; and Fig. 3 is a view similar to Fig. 2, but showin another embodiment of m invention.

eferrin articularly to ig. 1, a glass melting tan 1s designated as 7. The-tank is composed of a melting portion 8 to which is connected a refining portion 9 by means of a submerged throat 10 formed ina bridge wall 11, the tank having at its forward end a glass feeding forehearth 12. At the opposite end of the tank is indicated diagrammatically a do house 13. f y

eferring now to Figs. 1 and 2, resting upon a foundation indicated as composedl of common bricks 14.- is a structure of insulating bricks l15 lined upon its interior with a layer of highly heat resistantrefractory brick 16, such, for instance, as'those disclosed in'the United States Letters Patent of Paul G. Wi11eas,N0-. 1,605,885, patented Nov. 2, 1926. This structure defines the boundaries of the glass melting tank-8. In the bottom of the meltin tank yare a plurality of wells 17 extendmg substantially yacross the' tank.

These, as shown in Fig. 2, comprise two deep portions 17 a and a portion of lesser depth 176 connecting the two.

Centered over the deep portions of the wells 17 are openings 18a in theroof of-the tank. These openings are provided with refractory bushings 18 thrugh which extend electrodes 19 composed of carboniferous material, such as graphite. These velectrodes preferably are cylindrical in shape except for their lower ends which are enlarged'to form heads 21 having relatively large glass contacting surfaces. The openings 18a are larger inf diameter than the headsf21 of the lelectrodes so ,that the electrodes mayi be rreadily withdrawn from the tank. Surrounding the cylindrical portionof each electrode is a refractory covering or electrode holder 22 which is ofja material similar to the refractory brick 16. The holders 22 .have a sliding fit 4with the bushingsl 18. These coverings lit into groves in the heads 2110i the electrodes.

against th'e stein of the electrode.. If glass ua is used,.no sealing is necessary as the glass glass caused by .such oxide#- The cavities between the above the furnace will be -insuiciently heated v to bein other than a vsolid state.

.At the bottom of each of the dee er portions A17a of-the wells 17 is provide an outlet-23 through which the tanky may be drained. These are shown as filled vwith a( heat resistant granular substance 24 which acts as a plug to prevent the escape of glass. Obviously other forms odplugs may be used.

In the emb iment'of my invention shown inFig. 3, the Ashallow portion 17 b shown in the well 17 in Fig. 2j-is eliminated, and the well 26 (Fig. r3) is of uniform depth, this depth being suliicient to coverr the heads 21 of the electrodes 19. A resistor 27 of material which constitutes a conductor at all temperatures, as for example nichrome, is shown in placein the bottom of the well between the two electrodes. A holder 28 is indicated as attached to the upper end of one of the electrodes 19, and is provided with an opening 29 therein to provide means for attaching it to a chain or other positioning means. counterbalanced and lifted by anyvdesired means. v

With the above-described apparatus, new methods of operation suitable to the heating facilities available are possible. The prelferredmethod which may be used Where both electricity and an auxiliary heating means are found is to use .a tank ofthe type of construction shown -in Fig. 2. With the "electrodes 19 and theblocks 18 withdrawn temperature thereof to that suitable for melting glass within a short time. 1f a supply vof molten glass is available this may be poured into the heated wells. If a, supply of molten glass is not available glass-forming cullet may be. placed in the wells and vmelted by the use of the auxiliary heating means.' In either case the auxiliary heating `means is withdrawn and the blocks 18 and electrodes 19 replaced in the openings and the v current turned on, care being taken to totally submerge the heads of the electrodes'.

B the use of this method and the type of electrode disclosed above, it will be noted that the electrodes are only momentarily in'contact with the glass and air while they are being submerged. Thus any discoloration of the glass due to oxidation of the elecL trodes is avoided. With the electrodes submerged further glass-making cullet or. batch maybe added to the tank through the doghouse and the level of glass in the tank gradlly raised to the operative level.

. I auxiliary heating means are not avail- The electrodes obviously may bein a low fusible point, such as water-gla or soiu able, it is referred to use the type of tank shown in ig. 3. In such a tank a nichrome resistance element may be inserted between the heads of the electrodes, the walls and bottom of the well heated by passin current through the resistance element, e resistance element taken out, and glass havm silicate, may be introduced to fill a well. Thus the heads of the electrodes are again submerged without much, if any, oxidation thereo More lime or other materials can be added to the molten glass as the temperature is raised to bring the molten glass to the desired consistency. The process may then continue as in the, first described method.-

Optionally a resistance having a low melting point may be inserted in place lof the nichrome resistance element and withdrawn. through Vt-he openings 23 after la su ply of glass llas been added to submerge t e electrodes.

It is obvious that the material of the melted resistors and/or any .discolored glass which may form in the wells may readily be withdrawn through the openings 23 and fresh glass simultaneously added to maintain the electrodes submerged and to wash out the wells with comparatively litt-le waste of glass or time. Thus clean glass may be readily obtained without the loss of the large quantities of glass which occurred in the methods heretofore used.

IAfter the melting operations have been started by any of the above methods, I preferab-ly raise the electrodes as indicated in Fig. 2 to suitable points to obtain the most effective uniform heating of the glass batch.

As indicated, this movement of the electrodes is readily accomplished by the means 28 and 29 provided, and this arrangement enables me not only toinitially locate the electrodes at a particular depth but permits a regulation of the position of the electrodes in the bath to correct any improper conditions developing in the several vertical strata of the batch. 4

' During the operation, when one layer of the batch should tend to cool excessively,.the

yheads of the electrodes may be moved directly into that layer, thus shortening the path of the current therethrough and ,in-v

tensifying the heating effect therein.

It is obvious that many departures may be made from the above illustrated embodiments of my invention without departing from the spirit and scope thereof in the following claims:

I claim as my invention:

1. A glass melting furnace comprising a floor, wells in the floor for containing a relatively small amount of glass as compared with the capacity of the furnace, adjustable electrodes in alignment with said wells, means tively small amount as set forth for lowering the electrodes into the wells, and means for su plying a current of electricity to the electro es and through said lass while in 'said wells, whereby the starting of the furnace with a relatively small amount of molten glass is facilitated.

2. A glass melting furnace comprising a iioor, we ls in the floor for containing a relaof glass as compared the furnace, adjustable electrodes in ali nment with said wells, means for 'lowering t e electrodes into the wells, andl means to pass a current of electricity between the electrodes while in said wells, 'whereby'the starting of the furnace with a relatively small amount of molten glass is facilitated.

3. A glass melting furnace comprising a floor, wells in said floor for containing a relatively small amount of glass as compared with the capacity of the furnace, electrodes in said wells, and means to pass the current of electricity between said electrodesI beneath the plane of said floor, whereby the starting of the furnace with a relatively small amount of molten glass is facilitated.

4. A glass melting tank comprising a container for glass-forming materials, a second container for glass-forming materials within the first container, means for heating the second container, means for withdrawing the heating means, and a second heating means with the capacity of .for heating both containers and their contents whereby a relatively small amount of glass may be initially heated in said second container prior to the initiation of larger scale melting operations in the first-named container.

5. A lass melting tank comprising a container or glass-forming materials, a pluralit of containers for glass-forming ma- '.teria s within the first container, means for heating each of the plurality of containers, means for withdrawing the heating means, and a second heating means for heating all of the containers and their contents, whereby small scale glass melting operations may be carried on 1n said plurality of containers prior to the initiation of larger scale melting operations in all said containers.

6. A glass melting tank comprising a container for glass-forming materials, a plurality of containers for glass-forming materials within the first container, individually controllable means for heating each of the plurality of containers, and means for withdrawing glass from each of the plurality of contalners, whereby small scale glass melting operations may be carried on in said plurality of containers in starting the operation of th'e Y u igsom'vs said'plurality of containers with a minimum of glass loss from the tank as a whole.

' 7. The method of melting glass in a tank having a' plurality of containers for glassforming material in the door thereof which com rises heating glassfforming materials in t e containers-to a temperature at which it is molten, submerging electrodes in the molten mass, passing a current ofl electricity therethrough, adding additional glass-forming material to the tank to connect the masses in the containers with one anotherl and 'toy raise the glass in the tank to an operative level, heating the additional material y passing a current of electricity between the electrodes, and adjusting the height of the eleca trodes to regulate the path of travel of elec-- tricityl'` through the glass. f

8. he method of commencing the operation of a glass melting tank which comprises raisingthe temperature of small bodies of glassorming materials to a point at which the materials form a Huid mass, submergng electrodes in each mass, passing a current of v electricity between the electrodes l1n leach mass, and while maintaining the electrodes submerged addingadditional glass-forming material to interlconnect the small bodies of glass and raise the glass in the tank to an .so operative level.

9. The method of melting glass which comprises establishing within'a tank a relatively small pool of molten glass, thereafter suby merging spaced electrodes within the pool, passing'- a current of electricity' between the electrodes and through the glass, adding glass-making materials to the pool, and melt, ing the sameiby means of the current passe between said electrodes. Signed at Hartford, Connecticut this 2nd day of May, 1930.

HARGLD A. lDMAN 

